Chapter1 Introduction to Computers

What are computers? Computers are electronic devices that can follow instructions to accept input, process the input and then produce information. It is a machine that manipulates data according to a set of instructions.

Look inside the computer SOFTWARE HARDWARE

Computers are made of HARDWARE SOFTWARE

Hardware غير مطلوبة فقط للفهم

Hardware The parts of computer itself (tangible objects ) including : CPU (or Processor) and Primary memory (or Main Memory) Input devices i.e the keyboard and mouse Output devices Storage devices

The Case (System Unit or System Cabinet) غير مطلوبة فقط للفهم

Hardware Central Processing Unit (CPU) Input units Output units Memory (Main or Primary Memory & Secondary or Auxiliary Memory)

Components of a Computer System Central Processing Unit (CPU) Data control unit (CU) Memory Arithmetic logic Unit (ALU) output units RAM Input units ROM Auxiliary Memory Information/Knowledge

Hardware Organization Input Devices ... CPU memory motherboard hard drive غير مطلوبة فقط للفهم

Input Devices Translate data from form that humans understand to one that the computer can work with Most common are keyboard and mouse Selector Buttons

Examples of Input Devices 1. Keyboard (QWERTY keyboard, ATMs keyboard) ATM: automatic teller machine 2. Mouse 3. Scanner 4. Pre-storage Devise 5. Optical mark recognition (Light Pin , Bar code scanners) 6. Microphone 7. Joystick .

Examples of Input Devices(2) 8. Point and Draw devices 9. Trackball 10. Touchpad 11. Touch screen 12. Magnetic stripes and smart cars. 13. Digital Cameras

Hardware Organization CPU memory hard drive غير مطلوبة فقط للفهم

Mother-Board (or Main Board) غير مطلوبة فقط للفهم غير مطلوبة فقط للفهم CPU RAM ROM

Hardware Organization CPU memory motherboard hard drive غير مطلوبة فقط للفهم

Central Processing Unit (CPU) A specific chip or the processor a CPU's performance is determined by the rest of the computers circuitry and chips. The Central Processing Unit (CPU) performs the actual processing of data The speed (clock speed) of CPU measured by Hertz (MHz)

The CPU consists of : Control Unit (CU) Arithmetic and Logical Unit (ALU) Some Registers

Central Processing Unit (CPU) This is CPU Only: Central Processing Unit (CPU) Control Unit (CU) Arithmetic Logic Unit (ALU) Registers

coordinates all activities of the computer by: The Control Unit (CU) : coordinates all activities of the computer by: Determining which operations to perform and in what order to carry them out. The CU transmits coordinating control signals to other computer components.

consists of electronic circuitry to perform: The ALU : consists of electronic circuitry to perform: Arithmetic operations (addition, subtraction, multiplication and division) Logical operations (and, or, not, …) and to make some comparisons (less-than, equal, … etc.)

Hardware Organization CPU memory motherboard hard drive غير مطلوبة فقط للفهم

Primary Memory Memory (fast, expensive, short-term memory): Enables a computer to store, at least temporarily, data, programs, and intermediate results. Two general parts: RAM ROM

RAM (Main Memory) its a primary storage or random access memory (RAM). it temporarily holds data and programs for use during processing (volatile) Any information stored in RAM is lost when the computer is turned off. RAM is the memory that the computer uses to temporarily store the information as it is being processed. The more information being processed the more RAM the computer needs. RAM consists of locations or cells. Each cell has a unique address which distinguishes it from other cells.

Main Memory Address Memory locations 1 2 3 n Memory Cell

Main Memory

ROM: Read Only Memory ROM is part of memory Programmed at manufacturing time Its contents cannot be changed by users It is a permanent store Q: Mention some examples of ROM? A: (PROM & EPROM )

Other Kind of Memory PROM: Programmable Read Only Memory. EPROM: Erasable Programmable Read Only Memory Cache Memory Registers: not part of the main memory. Q : Registers are part of “ …… ” ?

Secondary Storage Stores data and programs permanently: its retained after the power is turned off Examples Hard Drive (Hard Disk) Located outside the CPU, but most often contained in the system cabinet Floppy Disk Optical Laser Discs CD-ROM, CD-RW, and DVD

Kinds of Disk Drives

Common Secondary Media Diskettes Data represented as magnetic spots on removable flexible plastic disks Most common size is 3 1/2 inches, in a rigid plastic case Disk drive holds the diskette, reads or retrieves the data and writes or stores data

Common Secondary Media Hard drive Data is represented magnetically as with diskettes Normally more than one rigid platter in a sealed unit These disks are not removable Significantly more capacity and faster operating than diskettes

Common Secondary Media Hard drive

Hardware Organization CPU memory motherboard hard drive غير مطلوبة فقط للفهم

Common Secondary Media Optical Laser Discs CD ROM & DVD’s Data is represented as pits and lands Some kinds are read only (CD-ROM) and some Kinds are rewritable (CD-RW) Significantly more capacity and faster operating than diskettes DVD: Digital Video Disk

Approximate printed 8.5 x 11 inch pages Common Secondary Media Approximate printed 8.5 x 11 inch pages Amount of storage Disk size 180 pages 360 Kb 5.25 low density 360 pages 720 Kb 3.5 low density 600 pages 1.2 Mb 5.25 high density 720 pages 1.44 Mb 3.5 high density a small library 700 MB CD a feature length movie 8.5 GB DVD

Common Secondary Media tapes Panasonic's LS120 3.5 inch diskettes Iomega's Zip & Jazz disks VCR tape (Video Cassette Recorder ) Flash USB disks MMC (Multi Media Card ) SD

The benefits of secondary storage can be summarized as follows: Capacity. Organizations may store the equivalent of a roomful of data on sets of disks that take up less space Reliability. Data in secondary storage is basically safe, since secondary storage is physically reliable.

Convenience. With the help of a computer, authorized people can locate and access data quickly. Cost. It is less expensive to store data on tape or disk (the principal means of secondary storage) than to buy and house filing cabinets.

Hardware Organization CPU memory hard drive غير مطلوبة فقط للفهم Output …

CPU Output Devices Pieces of equipment that translate the processed information from the CPU into a form that humans can understand. Processed information

Output Devices Monitors Printers Dot matrix printers Ink jet printers Laser printers Sound Blasters (Sound Card By Creative Lab) Controlling other devices

Software The instructions that tell the computer what to do Application Software - helps end-users perform general purpose tasks System Software - enables application software to interact with the computer

System Software System Software Operating System The most important is the Operating System Examples of operating systems: Windows XP, DOS, Apple, UNIX

System Software The software that controls everything that happens in a computer. Background software, manages the computer’s internal resources Resources examples : CPU, RAM , I/O devices, …

Among other things, the operating system: All hardware and software are under the control of the operating system. Among other things, the operating system: Determines how valuable RAM is allotted to programs. Performs tasks related to file management. Sets priorities for handling tasks. Manages the flow of instructions, data and information to and from the processor (CPU).

Examples of Microcomputer Operating System Software DOS - original standard for IBM compatibles Windows - a graphical operating environment Windows VISTA, XP, millennium, 2000, 98, and 95 Continue …

Examples of Microcomputer Operating System Software Cont. Windows NT - for powerful workstations & networks OS/2 - competitor to Windows 2000 Macintosh Operating System Unix - originally for minicomputers, now used on microcomputers and Internet servers Question: List some examples of operating systems ?

Application Software Packaged Custom Packaged - “off the shelf”, pre-written programs ( General purpose) Custom - written for an organization’s specific purpose (Special purpose)

Application Software – Basic Tools Word processors– example: Microsoft word Spreadsheets-- example: Microsoft Excel Database managers-- example: Microsoft Access Graphics-- example: Photoshop Spreadsheets: Computer software that allows the user to enter columns and rows of numbers in a accounting book like format.

Units of Measurements Bit (Binary Digit)(takes two values: 1 or 0) Byte = 8 bits KB (Kilo-byte) = 1024 bytes MB (mega-byte) = 1024 KB GB (giga-byte) = 1024 MB TB (Tera-byte) = 1024 GB Remark: 1024=210

Four Kinds of Computers Microcomputers 2. Minicomputers 3. Mainframe computers 4. Supercomputers

Comparison between the previous kinds of computers may made based on : Price Processing Speed Storage Capacity Powerful Single-user or Multi-user Supporting hundreds (or thousands) of users simultaneously Computer Size Companies size …etc.

Microcomputer =>Personal Computer => PC There are 3 types of the Microcomputers : Laptop Desktop Workstation

Personal Computer: A small, single-user computer based on a microprocessor. Workstation: A powerful, single-user computer. A workstation is like a personal computer, but it has : a more powerful microprocessor and, in general, a higher-quality monitor.

Minicomputer, Mainframe, and Supercomputer Minicomputer: A multi-user computer capable of supporting up to hundreds of users simultaneously. Mainframe: A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously. Supercomputer: An extremely fast computer that can perform hundreds of millions of instructions per second.

Desktop Computer Small enough for a desktop, but not easily portable Personal computers (PC’s) run general purpose software and are employed by a wide spectrum of users

Desktop Computers Cont. Workstations are powerful machines, running more advanced software, for technical, scientific, or data-intensive tasks These distinctions, however, are blurring

Portable Computers Easily transported from one place to another

Portable Computers Four categories Laptops Notebooks Sub-notebooks Personal Digital Assistants (PDA) Q: list all portable computer categories?

PDA

Minicomputers Desk-sized More processing speed and storage capacity than microcomputers General data processing needs at small companies Larger companies use them for specific purposes

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Mainframe Computers Larger machines with special wiring and environmental controls Faster processing and greater storage than minicomputers Typical machine in large organizations

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Supercomputers The most powerful of the four categories Used by very large organizations, particularly for very math-intensive types of tasks

Supercomputers

Characteristics of Computers 1- Store a large amount of data and information for a long period of time. 2- process data and information in high accuracy level . 3- Speed in processing data information. 4- Sharing of information / network.

Understanding the difference between Data, Information and Knowledge: Computer Data Information Knowledge

Data: is the name given to basic facts such as names and numbers. Information: is data that has been converted into a more useful or intelligible form. Knowledge: arrangement of information and classifying information of the same type or the same topic.

Data Data: are details of various types of transactions and details relating to specific situations, which are input to a data processing system (e.g. computer) for processing in a prescribed way. Examples of data relating to students are student-number, student-name and grades.

e. g. -2 4 0 -3 10 (data) | | sort \ / -3 -2 0 4 10 (information)

Data Document files Worksheet files Database files

Information Information: the result of processing data. Information: Must serve a useful purpose Must be of an acceptable level of accuracy Must be available at the right time Must be relevant to the enterprise, person, … etc.

Knowledge Putting a number of information with the same type or same topic would be a knowledge.

Processing data produces information, and processing information produces knowledge.

Computer Viruses

Computer Viruses A computer virus are small software programs that are designed to spread from one computer to another and to interfere with computer operation. A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.

Examples of Viruses Win32/Conficker INF/Autorun Win32/PSW.OnLineGames n32/Agent

Viruses and Virus Protection A virus program Infects programs, documents, databases and more … It is man-made It can hide and reproduce It can lay dormant (inactive) and then activate Anti-virus programs can help

Types of Computer Viruses Macro Viruses A macro virus, often scripted into common application programs such as Word or Excel, is spread by infecting documents. Network Viruses rapidly spreads through a Local Network Area (LAN), and sometimes throughout the internet. •Trojan Horses The Trojan virus once on your computer, doesn't reproduce, but instead makes your computer susceptible to malicious intruders by allowing them to access and read your files. Making this type of virus extremely dangerous to your computer's security and your personal privacy.

Types of Computer Viruses Logic Bombs a piece of code that are inputted into a software system. When a certain and specific condition is met, such as clicking on an internet browser or opening a particular file, the logic bomb virus is set off. Companion Viruses takes advantage of MS-DOS. This virus creates a new file with typically the .COM extensions, but sometimes the .EXD extension as well.

Types of Computer Viruses Boot Sector Viruses generally hide in the boot sector, either in the bootable disk or the hard drive. Unlike most viruses, this virus does not harm the files in the hard disk, but harm the hard disk itself. Multipartite Viruses spreaded through infected media and usually hides in the memory. Gradually, the virus moves to the boot sector of the hard drive and infects executable files on the hard drive and later across the computer system.

Sources of Computer Viruses Three primary sources The Internet Via downloads and exchanges Diskettes Exchanging disks Computer networks Can spread from one network to another

How do you know if you have a virus? Lack of storage capability Decrease in the speed of executing programs Unexpected error messages Halting the system

Virus Protection The software package distributed with new PCs always includes an antiviral program. The best way to cope with viruses is to recognize their existence and use an antiviral, or antivirus program.

Some tips that will help minimize your vulnerability to viruses: Delete e-mails from unknown or suspicious, untrustworthy (unreliable) sources, especially those with files attached to an e-mail. Never open a file attached to an e-mail unless you know what it is, even if it appears to come from a friend. Download files from the Internet only from legitimate and reputable sources. Update your antivirus software at least every two weeks as over 200 viruses are discovered each month. Backup your files periodically Traditionally virus protection has been at the PC or client level. However, this may change as companies look to network and Internet service providers for more services.